The invention is based on a rotary position transducer for generating electrical rotational angle signals as a function of the swiveled position of a rotating device, in particular a throttle valve in a fuel supply system of an internal combustion engine.
A known rotary position transducer of this type (German Patent 21 11 262), a so-called acceleration signal transducer, serves to affect the control electronics in a fuel injection system, so that fast acceleration from low rpm is possible. In this acceleration signal transducer, two concentric contact tracks are disposed, insulated from one another, on a printed circuit board that is secured to the stationary carrier embodied as a metal base plate. The two contact tracks are provided with radial transverse ribs with teeth facing one another. A wiper secured to a wiper plate seated rotatably on a bush retained in the base plate cooperates with the two contact tracks. The wiper plate has a radially protruding support arm with two stop bolts disposed side by side spaced apart from one another in the direction of rotation. One stop bolt carries the wiper on the underside of the wiper plate; the wiper rests on the contact tracks with axial biasing. The wiper plate and thus the wiper is rotated by a coupler, which protrudes through the bush in the base plate and has a receptacle for inserting the end of the throttle valve shaft, which is held in it in a positively engaged manner. The coupler has a radially protruding coupler fork, which carries with it, in both directions of rotation, an indexing arm pivotably seated on the support arm of the wiper plate; this arm in turn protrudes between the stop bolts on the support arm. Upon rotation of the throttle valve, the coupler fork rotates the indexing arm, which via the stop bolts rotates the wiper plate with the wiper. The wiper slides over the contact tracks, alternatingly contacting one transverse web belonging to one or the other contact track, and as a result tripping control pulses in the control electronics.
Because of the fixed coupling of the coupler and the throttle valve shaft, on the one hand, and the coupler and the wiper plate, on the other hand, all the radial and axial oscillations of the throttle valve shaft are transmitted to the wiper position. This can cause locally high wear on the contact tracks, particularly in the geometrically defined end positions. This wears away the contact track and/or wiper severely and causes functional problems.